The present invention pertains to a process for the preparation of aromatic polyesters and more particularly pertains to a process for the preparation of aromatic polyester via a metal-mediated carbonylation and coupling reaction of an aromatic trifluoromethane sulfonate reactant and a diol.
Aromatic polyesters are widely used commercially and are commonly prepared by each of the following processes: (1) esterification of a hydroxycarboxylic acid, (2) esterification of a diol and a diacid, (3) ester interchange with an alcohol, (4) ester interchange with an ester, (5) esterification of acid chlorides, or (6) lactone polymerization. Ester interchange methods are often used because methyl esters are easier to purify than the diacids or diacid chlorides and by-product methanol is easily removed by distillation. These processes generally require the use of high temperatures, for example, in the range of 260.degree. C., for polymer formation. This high temperature requirement has a number of shortcomings, the most notable is increased energy consumption. An alternative process for the preparation of aromatic polyesters is disclosed in U.S. Pat. No. 4,933,419 to R. J. Perry and S. R. Turner. That process is a palladium catalyzed carbonylation and coupling of diols and dioodoaromatic polymeric esters, which can be performed at lower temperatures than ester interchange methods. That process, however, requires diiodo compounds and produces by-product hydrogen iodide. Recycling of iodide can present practical difficulties.
Ester formation from trifloromethane sulfonates is reported in Dolle et al, Journal of the Chemical Society, Chemical Communications, (1987) pp 904-905 and Cacchi, S., et al, Tetrahedron Letters, Vol. 27, No. 33, (1986) pp 3931-3934. Neither of these publications teaches or suggests the preparation of polymers.